Previous research on tolerance to effects of cocaine on operant behavior in rats and monkeys has revealed tolerance contingent on whether the drug is given pre or post session. A recently published experiment with pigeons, and the preliminary study did not find that tolerance was similarly contingent on when the drug was administered. The proposed research will further examine the role of behavioral factors and pharmacological factors in the development of tolerance to cocaine in pigeons through three experiments. Experiment 1 will examine the contributions of eating while under the effects of cocaine to the development of tolerance to cocaine during a preceding operant behavioral session. Experiment 2 will examine effects of mere drug exposure without exposure to a behavioral session in the development of tolerance to cocaine during a behavioral session. Experiment 3 will examine effects of acute and chronic cocaine administration on the pharmacokinetics of cocaine. This program of research will examine the role of behavioral factors, including the experimental session and eating, and pharmacological factors in the development of tolerance to behavioral effects of cocaine in pigeons. [unreadable] [unreadable] [unreadable]